If you mention a stock ticker, that word on your blog will typically contain a mouse-over effect that will display a Yahoo Finance chart. Or if you have an address, they might show you a Yahoo Map. Yahoo integrated the plugin with web search, maps, finance, product search, Flickr, Yahoo Autos, news search, and more. For more details, visit http://shortcuts.yahoo.com/.
Oh, and if you are one of the first 500 bloggers to integrate this into your WordPress blog, you can get a free t-shirt.